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4 • Prosthodontics
127
from the cast. The stone is removed to a depth that is predetermined by the probing depth around the teeth and
information from any radiographs. In a flanged denture,
the stone is trimmed to simulate the ridge following tooth
extraction.
Surgery
In extreme cases, surgery (septal alveolotomy and labial
alveolectomy; very rare nowadays) of the ridges is undertaken at the same time as tooth extraction. This may be
indicated if there is a large particularly labial undercut or
if marked repositioning of the teeth is to be undertaken. It
is undesirable to remove the cortical plate of bone as it accelerates bone resorption.
Review Appointments
It is important to review a patient with an immediate denture at regular intervals especially in the first few weeks and
months. The initial days are primarily concerned with the
postoperative care of the healing tooth sockets, while the
later reviews are directed at the management of the resorption. Advice on ensuring that the denture is not removed for
the first 24 hours will help limit any inflammatory changes.
These changes may become a problem where the denture is
left out of the mouth for any length of time and reinsertion
then becomes either painful or intolerable. A 24-hour review is therefore essential to make appropriate adjustments.
A timeline of reviews is suggested as follows:
At 24 hours: a general check is made of the overall comfort
of the dentures and to ensure no major ulceration has
occurred and that the clot is still in situ.
At 1 week: a more detailed check and adjustment of den-
tures can be made.
At 1 month: the socket has healed and a chair-side tempo-
rary reline may be required.
At 3–6 months: the management of loss of fit of the den-
tures owing to bone resorption is undertaken; this may
involve relines and/or rebases, which are undertaken at
either the chair side or with the aid of the production
laboratory.
At 12 months: a replacement denture is made using the
copy denture technique.
There is no evidence base available to suggest that an imme-
diate denture technique is of any clinical benefit although
clearly this is an area that has gained much attention recently in the implant field.
4.4 Overdentures
beneath its impression surface. Dental implants have created a new category of overdentures, namely the implantretained or implant-supported overdenture. This section
focuses on tooth-supported overdentures but analogies
can be drawn for implant-retained or implant-supported
overdentures.
The need for meticulous planning is necessary when undertaking the use of precision attachments in tooth-borne
overdentures, their use increases complexity as well as both
financial and biological cost.
INDICATIONS
n
Converting a partially dentate individual to complete
dentures
n
Elderly patient with a few remaining teeth and a mucosal-borne partial denture
n
Severe attrition/erosion/abrasion
n
Cleft plate and surgical defects
n
Hypodontia
n
Potentially difficult complete denture requirements
CONTRAINDICATIONS
n
Poor oral hygiene
n
Rampant uncontrolled caries in the remaining dentition
n
Uncontrolled periodontal disease
n
Inadequate interarch space
ADVANTAGES OF OVERDENTURES
n
Maintenance of alveolar bone
n
Proprioceptive feedback
n
Assistance in control of masticatory force; a patient with
an overdenture is able to exert higher forces during mastication with more precision
n
Recognising size and texture of objects
n
Position of mandible during function
n
Minimal load thresholds
n
Reduction of psychological trauma
The ideal overdenture scenario would be the retention of
four root-filled teeth in the lower arch, the canines and
the first molars. This situation, however, is highly improbable as the first molars are commonly among the first
teeth to be lost and, therefore, are unlikely to be one of
the four remaining teeth. The canines are important
teeth as they have long roots and are highly proprioceptive but also command an important position in the line
of the arch.
LEARNING OBJECTIVES
You should:
• understand the advantages of overdentures over more
conventional dentures
• acknowledge the different overdenture preparations
that can be prepared and the advantages and disadvantages of each.
An overdenture is a prosthesis that gains additional support
by covering one or more teeth, prepared roots or implants
ABUTMENT
Abutment selection depends upon: (Ettinger (2004))
n
periodontal status
n
number and location in arch
n
canines and molars where possible
n
conservation status
n
need for root canal therapy
n
presence of bony undercuts
n
extra retention from teeth
n
economics.
128
Master Dentistry
PERIODONTAL DISEASE
With respect to periodontal disease in patients wearing
overdentures, it has been shown that:
n
35% show a significant loss of attachment within the
first 3 years
n
only 50% of dentures are plaque free, and the majority
of patients wear their dentures at night
n
disease is related to both poor denture and poor oral
hygiene.
Caries prevalence within 5 years of placement in studies
of overdenture abutments varies from 13% to 35%. The use
of topical fluoride is indicated for these patients, which may
be delivered as fluoride varnish at maintenance and recall
visits. The daily use of a high fluoride toothpaste is the most
cost-effective form of delivery.
Preparation of Coronal Root Surface
Table 4.3 describes various preparations of the coronal root
surface for overdenture placement.
The presence of overdenture abutments allows the loads
from occlusal forces to be dissipated over a larger area as the
support of the periodontal ligament is brought into function. This along with the increase in tactile discrimination
and the maintenance of alveolar bone levels make the benefits of this technique invaluable in dealing with certain
clinical denture problems.
The use of implant-retained or implant-supported lower
overdentures particularly in the mandible is becoming more
widespread. An atrophic mandible can be prosthetically
very difficult to manage; planning to maintain residual alveolar ridge using dental implants or retained roots confers
significant benefit, enhanced retention and improved
stability, for a patient who would otherwise have to cope
with the limitations of a conventional complete denture.
Evidence Base for This Clinical Approach to Overdenture Denture Construction (Crum and Rooney 1978)
n
Patients with complete maxillary dentures and mandibular overdentures showed a mean vertical reduction
of 1.8 mm for the anterior part of the maxilla and
0.6 mm for the anterior part of the mandible over a period of 5 years postextraction compared to vertical bone
loss on the maxilla of 1.7 mm, while the mandible
showed 5.2 mm of bone resorption in conventional patients over the same 5-year period.
n
The findings were taken at yearly intervals and showed
that the greatest portion of the loss of alveolar bone (approximately 50%) occurred during the first year after
extractions.
n
This work has been replicated numerous times since in
patients with implant-retained or implant-supported
overdentures.
The McGill Consensus Statement on Overdentures (Feine et al 2002)
The evidence currently available suggests that the restoration of the edentulous mandible with a conventional denture is no longer the most appropriate first-choice prosthodontic treatment. There is now overwhelming evidence
that a two-implant overdenture should become the first
choice of treatment for the edentulous mandible.
Mandibular Two Implant-Supported Overdentures
as the First Choice Standard of Care for
Edentulous Patients – The York Consensus
Statement (Thomason et al 2009)
With the advent of dental implants there is now more than
one available treatment for edentulous patients. Current
evidence suggests that the restoration of the edentulous
mandible with a conventional denture is a much poorer
alternative than the use of an implant-supported prosthesis. There is now a large body of evidence that supports the
proposal that a two–implant-supported mandibular overdenture should be the minimum offered to edentulous
patients as a first choice of treatment.
4.5 Removable Partial Dentures
LEARNING OBJECTIVES
You should:
• understand the basic concepts of partial denture con-
struction
• appreciate the importance of design for the prevention
of further dental disease
• be able to classify and describe a partial denture using
terminology that will be understood by colleagues.
Treatment planning for partial dentures should follow an
assessment of the oral health of the patient. Partial dentures
carry significant risk in terms of increasing risk for both caries and periodontal disease. The provision of a partial denture should consider the benefits as well as the risks, and all
Table 4.3 Preparation of the Coronal Root Surface for Overdenture Placement.
Preparation Advantages Disadvantages
Flat facing Plenty of occlusal clearance; no lateral forces applied; easy to
Dome-shaped
facing
Thimble-shaped
facing
RCT
, Randomised controlled trial.
place attachments
Favourable crown:root ratio; efficient plaque control; sufficient
occlusal clearance
Provides maximum retention and stability; RCT may not be
required; patient is aware that a tooth still remains
Risk of gingival overgrowth; difficult to keep clean; no real
additional stability
RCT normally required; may provide less retention and
stability than thimble shape
May be insufficient occlusal clearance; unfavourable crown:
root ratio; minimal room for attachment placement; protection
of tooth surface may be required
alternatives should be discussed with the patient. The need
for ongoing maintenance and the responsibilities of the patient in order to maintain and enhance their oral health
should be explored. Each partial denture should be designed
specifically for each patient, taking into account the capacity of the patient. Consider what appropriate professional
support would be required to maintain their oral health encumbered by a partial denture, more importantly the risks
and benefits to a patient (of a partial denture) where their
capacity to maintain their dentition is impaired, even with
appropriate professional support. Fixed alternatives and implants may be of greater benefit, as indeed may accepting
the status quo and not providing a partial denture. Not all
missing teeth should be or indeed need to be replaced. Stabilisation of existing disease should be undertaken before embarking upon prosthetic treatment, unless incurring a delay
would be detrimental to the wellbeing of the patient, where
a provisional or interim denture is advisable to restore aesthetics and function. Preliminary impressions are taken for
the planning and design of the partial denture. The resulting models will require mounting on an articulator prior to
design. There might be significant advantage in undertaking these during the stabilisation of disease as the design of
the denture may influence treatment planning, for example,
rest seats incorporated into class II restorations, full veneer
crowns contoured to provide undercut areas for retention or
tooth extraction as a result of overeruption.
Partial denture design intends to:
n
preserve what remains
n
restore what is missing
n
prevent future disease.
When making a partial denture, the following questions
need to be addressed:
n
Is the prosthesis necessary?
n
Is the patient healthy?
n
Is the patient suitable for the prosthesis?
n
How large a space is to be restored?
n
By what structures is the prosthesis to be supported?
n
How is the prosthesis to be made?
PARTIAL DENTURE CLASSIFICATION
A simple and effective classification is one that describes
partial dentures in terms of the nature of the support
utilised by the partial denture:
n
Teeth – the only true tooth-borne removable prosthesis is
a telescopic bridge
n
Mucosa
n
Teeth and mucosa.
Further information can be gained by a classification of
the partially edentulous arches which relates the edentulous
spaces to the remaining teeth (Fig. 4.5; Kennedy 1928).
The following points should be noted when using this
classification:
n
The most posterior edentulous area determines the class.
n
Additional edentulous areas are called modifications.
n
The size of the modification is not important.
n
If a third molar is missing and not to be replaced, it is not
considered in the classification.
4 • Prosthodontics
Class 1 Class 2
Class 3
Class 3 Modification 1 Class 2 Modification 2
Fig. 4.5 Classification of the partially edentulous arches. Class 1, bilateral
free-end saddles; class 2, unilateral free-end saddle; class 3, unilateral
bounded saddle; class 4, single-bounded saddle anterior to abutment
teeth. Class 3 modification 1 shows an additional bounded saddle; Class 2
modification 2. A unilateral free end saddle with two additional bounded
Class 4
129
PRELIMINARY IMPRESSIONS
This preliminary impression will be used to produce a preliminary model which in turn is used to fabricate a special
tray, record blocks for the recording of a preliminary registration and then to be surveyed in the process of designing
the final partial denture. For this reason these preliminary
impressions need to be evaluated with each of these clinical
stages in mind. The clinician should be discerning in what
constitutes an adequate impression fit for each of these
purposes and to avoid the temptation of thinking, ‘I can
compensate when using the special tray’. A special tray
compromised in quality by the standard of the preliminary
impression will produce a final impression which is then
likely to be compromised. One of the greatest challenges in
recording a preliminary impression for a partial denture is
ensuring that the stock tray is able to record both the dental
hard tissues and the alveolar hard and soft tissues. There is
often significant vertical difference between occlusal and
incisal levels and the vestibular and buccal sulcus depths. It
may very well be desirable to modify the stock tray with
impression compound or silicone putty to support alginate.
This should ensure recording of all the features required to
support and retain the final partial denture.
LABORATORY PRESCRIPTION
The prescription on the laboratory card must be clear and
comprehensive. If there is any possibility of confusion, it is
130
Master Dentistry
essential to discuss the case personally with the technician
involved. If preliminary record blocks are required they
should be stable and rigid enough to support a wax rim
without danger of distortion either by occlusal loading or
the effects of prolonged exposure to the oral environment.
Special tray design should be compatible with the impression material and technique to be deployed for the working
impression. If the laboratory card is not completed and
dated, work may not be available for the next appointment.
DESIGN
The design of a partial denture should always be determined before the master impressions are recorded. In this
respect, the preliminary casts should be mounted on an
articulator and surveyed prior to producing the desired design. In some cases where there are sufficient teeth, casts
can be placed in occlusion by hand prior to mounting. In
other situations, it will be necessary to construct occlusal
rims to register the jaw relationship of the patient. A provisional design should then be produced and, at this stage, a
decision should be made on the need for possible tooth
preparation or modification.
This may indicate that the following may be necessary:
n
Rest seat preparation to provide sufficient space and
horizontal surface for any support component.
n
Modification of tooth contour preparation to lower survey lines or the addition of light-cured composite resin to
create adequate retentive undercuts for clasp arms.
n
Altering the path of insertion to enhance retention
along the path of natural displacement.
n
Preparation of guide planes designed to facilitate paths
of insertion or eliminate dead spaces at the abutmentsaddle interface.
The proposed design should then be transferred to the
laboratory prescription and study cast, which should be
retained for reference until the trial stage has been completed. The design prescription must be clear and comprehensive. The design will describe:
n
saddles
n
support
n
retention
n
bracing and reciprocation
n
connector
n
path of insertion.
Second Clinical Visit
Normally, the second visit will be devoted to recording the
jaw relationship of the patient prior to mounting casts on
the articulator and developing a design. However, the second visit may be for master impressions where the occlusion is sufficiently clear for the casts to be mounted and a
design determined.
Recording Jaw Relationships
For the purpose of jaw relationships and their registration,
partially dentate patients can be divided into two categories:
1. Patients without an occlusal stop to indicate the correct
intercuspal position or vertical dimension of occlusion
2. Patients with occlusal contact in the intercuspal position.
If an occlusal stop is present in the mouth, it may be that
the associated intercuspal position is acceptable. If there is
horizontal deviation of the mandible after the initial occlusal contact, it may be necessary to correct the deflective
occlusal contact by tooth modification. If there is no stable
contact or loss of occlusal vertical dimension (OVD), the
appropriate OVD will have to be determined by adjusting
occlusal rims in relation to the rest vertical dimension
(RVD). The OVD is determined by establishing the RVD and
modifying the occlusal rims until the OVD is some 2–4 mm
short of the RVD, this distance indicating the amount of
interocclusal clearance. The horizontal jaw relationship
recorded should be the retruded position. Box 4.2 outlines
the procedure.
Occlusal Contact in Intercuspal Position
If there is occlusal contact, the rims should be adapted until
the natural occlusal contact is observed (Box 4.3). These
may be checked visually, by asking the patient if there is
even contact, using articulating paper and shimstock.
Shimstock is valuable when determining contacts in cases
with deep overbites and long labial palatal contacts which
cannot otherwise be easily seen.
Box 4.2 Technique to Establish Jaw
Relationships in Patients With an Occlusal Stop.
1. Occlusal rims should be supported by a temporary base made
to resist both thermal and mechanical distortion. Care should
be taken to ensure wax does not fracture or delaminate.
2. In the mouth, the fit and extension of the rim should be
modified if necessary to produce acceptable stability.
3. Occlusal contacts should be recognised with the natural
teeth in occlusion.
4. The upper occlusal rim should be adjusted so that the occlusal plane is appropriate in relation to the remaining upper
natural teeth.
5. If when the patient closes the occlusion shows a premature
contact between a tooth and the opposing occlusal rim, the
offending part of the rim should be adjusted until the occlusal
stop is re-established. If there is an anterior saddle, the rim
must indicate the correct incisal level and degree of lip
support. Removal of wax from the palatal aspect of this rim
might be necessary in order to allow closure of the mandible
into the tooth position while retaining the incisal level.
6. The lower rim should then be adjusted until the occlusal stop
has again been established.
7. Wax should be removed or added from the buccal and
lingual surfaces of the rims align with the natural teeth.
8. The lower rim should be modified so that there is a small
gap (about 1 mm) between the occlusal surface of the rim
and the opposing teeth or rim when the natural teeth are in
contact.
9. The intercuspal or retruded contact position should be
recorded using an occlusal registration material such as Bite
Registration Paste. This should be thin and only record the
cusp tips and incisal tips.
10. The casts should be placed in occlusion using the occlusal
rims and checked to determine that the tooth relationship
on the casts is the same as that in the mouth. Excessive
thickness of particularly elastomeric registration pastes will
lead to the wax rims springing apart.
11. Check if there is a premature contact between the heels of a
cast and the opposing block or cast, this should be eliminated.
4 • Prosthodontics
131
Box 4.3 Technique to Establish Jaw Relationships
in Patients Without Occlusal Contact.
1. The maxillary and mandibular rims are trimmed to conform to
selected reference points for the remaining natural dentition.
2. The lower rim should be adjusted until there is an even occlusion
along the retruded arc of closure at the chosen occlusal vertical
dimension. Allowing adequate freeway space between the
record blocks at rest.
3. Locating notches should be cut in both rims, a thin and even
application of registration paste applied to the occlusal surface
of the lower rim, and the patient guided into their path of
retruded closure.
Laboratory Prescription
The prescription will cover a number of points. If the next
stage is the try-in of a metal framework, the design should
be drawn on the laboratory card and full instructions given,
including the path of insertion decided by the clinician.
Shade, material and mould of artificial teeth should be chosen if the next stage is try-in. It is advisable to undertake
framework try-in separately to the tooth setup try-in.
MASTER IMPRESSIONS
Master impressions are obtained at the second or third
clinical visit. A suitable impression material is selected
based on accuracy and, particularly if the impressions are
not being cast promptly, dimensional stability.
Stops may be placed on the fitting surface of the individual trays before correcting peripheral extension. These will
aid in ensuring an adequate thickness of the impression
material. When free-end saddle areas are present, border
moulding should be undertaken:
n
The study casts should be retained as a guide for the
technician.
n
If the metal denture is restoring lower free-end saddles,
consider the need for the altered cast technique (see later):
if the technique is to be employed, request the addition of
acrylic trays to the framework in the saddle areas.
The impression is recorded as described in Box 4.4.
Laboratory Prescription
The laboratory prescription should indicate that casts are to
be poured in hardened dental stone. Bearing in mind that
the occlusion has already been determined naturally or by
occlusal rims prior to establishing a design, the subsequent
stage should be either trial dentures or the production of a
metal casting. In the former situation, a shade and mould
of teeth must be selected.
The Metal Framework
1. The framework must conform to the original design.
2. The framework must fit the cast. If the fit is unsatisfactory
on the cast, it will also be unsatisfactory in the mouth.
3. The casting should be free from porosity or other imperfections.
Note: if any of the above points are not met, the casting
should be returned to the laboratory.
The position of the retentive and bracing arms should be
checked relative to the survey lines:
1. All components that are designed to be clear of the gingival margin area should be checked to ensure that the
clearance is adequate.
2. In the mouth, these aspects should be checked again,
remembering that the likelihood of some instability in
free-end saddle designs may be caused by spacing beneath the mesh retention.
3. The occlusion is examined to ensure that there are no
premature contacts; this should be done by visual examination, from comments by the patient and with the
use of articulating paper or disclosing wax. Any premature contact must be removed at this stage.
If the metal framework is satisfactory, request the setting
of the teeth on the framework after choosing an appropriate shade and mould of tooth.
Altered Cast Technique
The altered cast technique is an impression method designed to compensate for the differential support provided
by the abutment teeth and the mucosa of the edentulous
part of the alveolar ridge to a lower partial Kennedy I or II
denture base (Box 4.5).
In many cases there is no indication for the use of this
technique; indeed it is more often used to correct faults created by a suboptimal master impression.
THE TRIAL DENTURE
The trial denture is the last stage at which modifications
can be made before the wax is replaced by acrylic. A careful
Box 4.4 Recording the Impression.
1. The tray is dried and a thin layer of adhesive is applied to the
whole of the inner surfaces of the tray and to an area extending 3 mm beyond the periphery of the tray. The adhesive is
allowed to dry before loading the tray.
2. A low-viscosity alginate is used to record the impression. In
some cases, it may be beneficial to use silicone-based or
rubber-based materials.
3. If the impression is satisfactory, a cast should be poured in
improved hardened dental stone as soon as possible.
4. All individual trays should be retained until treatment is
completed.
Box 4.5 The Altered Cast Technique.
1. The cobalt–chromium (CoCr) casting is tried in the mouth to
ensure it adapts correctly.
2. A 0.6-mm fitting tray is added to the free-end saddle of the CoCr
framework and border moulded using an appropriate material.
3. The recording of an impression uses zinc oxide/eugenol, with
pressure only applied to the rest seat areas of the framework.
No direct pressure is applied to the edentulous saddle area.
4. The original master cast is sectioned, removing the posterior
part of the model that had recorded the free-end edentulous
ridge area.
5. The framework is seated back on the sectioned model and a
new posterior section cast into the tray area.
132
Master Dentistry
routine must be followed to prevent any mistakes continuing through to the finished dentures. The dentures should
be examined first on the mounted casts for:
1. fit of dentures on the casts
2. occlusion
3. position of artificial teeth with regard to adjacent natural ones
4. the arrangement of anterior teeth
5. extension and contouring of wax flanges.
The trial dentures are then examined in the mouth for:
1. fit of the dentures
2. occlusion and OVD
3. contouring of wax flanges with regard to peripheral extension, shaping of polished surface, coverage of gingival margins
4. appearance: modify positions of teeth and incisal edges
of anterior teeth to achieve a pleasing result that is
acceptable to the patient
5. patient’s comments on appearance: as seen in the
mirror and ensure that they are satisfied.
If, at this stage, the occlusion is incorrect, modifications
must be carried out before continuing with the next stages.
Consideration how best to correct this may range from minor chair-side adjustment of the acrylic teeth either within
the wax, to re-recording the occlusion and rearticulating
the casts, in which case it will be necessary to have a retry
to check that any changes are satisfactory.
Laboratory Prescription
Carefully list and describe any modifications you wish the
technician to carry out before finishing the dentures. Modifications at this stage should always be minor unless a retry
is to be undertaken.
To avoid problems on insertion of the final denture:
1. Undercuts should be blocked out in wax on master cast,
in respect of vertical path of insertion.
2. The master cast should be duplicated.
3. Denture should be processed on duplicate cast.
4. The processed denture should be fitted back onto the
master cast.
FINAL DENTURE INSERTION
The denture should be checked to see that there are no
sharp edges or acrylic ‘pearls’ on the fitting surface of the
saddle areas. Insert the denture into the mouth. Occasionally, the denture cannot be seated because acrylic has been
processed into an undercut area on the cast; this results
from inadequate blocking out of the undercuts. If the area
of acrylic to be removed is not immediately apparent, use
pressure relief cream. Always remove the acrylic by approaching with the bur from the fitting surface. The contact
between the denture and the tooth in the non-undercut
area should not need adjustment.
In the mouth, check:
1. fit of components
2. retention and stability
3. aesthetics
4. occlusion.
Occlusal contact is checked by asking for the patient’s
comments, by visual inspection and by the use of articulating paper. Articulating paper should be inserted bilaterally.
Occlusal adjustment should be continued until both the
patient’s comments and visual inspection confirm that even
contact has been achieved in intercuspal position. Attention should be given to occlusal contacts in lateral and
protrusive positions. In many patients, the dentures will be
adjusted so that they conform to the occlusal guidance provided by the remaining natural teeth.
Advice to the Patient
The patient must be shown and taught the correct way to
handle the denture for insertion and removal and vulnerable components must be pointed out. A printed sheet of instructions should be provided for the patient. This will mention, in particular, aspects such as cleaning/eating/wearing
at night/pain/need for regular recall, including recall with
the hygienist.
It is important to discuss these points verbally with the
patient first of all. The purpose of such a sheet is simply to
act as an aide-mémoire. Finally you should ensure that the
patient knows whom to contact in the event of problems
arising with the denture.
The responsibility for the prosthetic care of the patient
does not end with the insertion of a denture.
Review Appointment
The patient should be asked for comments on the first week
of wearing the dentures. A history must be taken of any
complaint. Subsequent examination must be directed to
diagnosing the cause of the complaint before making any
adjustments. Whether or not there are any problems reported by the patient, the denture-bearing tissues must be
examined and the occlusion must be checked. At times, a
patient may claim to be perfectly comfortable even though
extensive ulceration is present.
Any inflammation of the denture-bearing tissues that
is not related to the peripheral area is most likely from
occlusal causes. Therefore, a careful inspection must
be made of occlusal contact in tooth position and excursive movements, and the necessary adjustments made.
The impression surface of the denture should only be
adjusted where there is clear evidence of excessive pressure. Should attention of the impression surface be required, a disclosing material such as pressure indicator
paste should be used.
A check must be made on the patient’s oral and
denture hygiene. This can be done with the use of a disclosing solution. Steps to reinforce plaque control must be
taken.
Evidence-Based Approach to the Provision of Partial Dentures (Graham et al 2006)
1. Existing research suggests that 30–50% of patients who
are prescribed a removable partial denture (RPD) never
or only occasionally wear the prosthesis.
2. This study has identified key factors that influence pro-
fessional provision and patient use of RPDs.
4 • Prosthodontics
133
3. For patients, wearing an RPD is not simply a matter of
aesthetics, but of avoiding the social stigma associated
with tooth loss.
Why Do Dentists Struggle With Removable Partial Denture Design? An Assessment of Financial and Educational Issues (Lynch and Allen 2006)
1. Financial factors did not have as significant an effect on
the quality of prescription and fabrication of cobalt–
chromium removable partial dentures (CCRPDs) as
compared to educational factors.
2. Serious deficiencies in the teaching of CCRPDs during
vocational training were identified, and these deficiencies lead to deskilling of newly qualified dentists.
Self-Assessment: Questions
MULTIPLE CHOICE QUESTIONS (TRUE/FALSE)
1. Complete denture assessment should include:
a. A history of tooth loss
b. A denture history
c. A medical history
d. A social history
e. A summary of the patient’s expectations
2. Impression compound contains:
a. Stearic acid
b. Borax
d. Paraffin wax
e. Copper
3. An immediate denture is advisable for:
a. A single tooth replacement in the anterior region of
the mouth
b. A patient who will require the surgical removal of
the broken down tooth
c. A patient who is at risk of tooth movement if a
replacement unit is not placed soon after extraction
d. A patient losing an upper second molar tooth
e. A case where haemorrhage control may be required
4. A partial denture clasp made of cast cobalt–chromium:
a. Should not be used as an occlusally approaching
clasp arm on a premolar
b. Is more flexible than a wrought gold clasp of similar
length
c. Engages 0.5 mm undercut
d. Is a potential food trap
e. Can be circumferential, occlusally approaching or
gingivally approaching in design
5. The altered cast technique is used to:
a. Account for the differential compression between
hard and soft tissues
b. Remount flasked dentures to perfect the occlusion
c. Destroy unwanted models
d. Construct a master cast that is altered by partial
replacement with a cast of an additional impression
e. Modify a cast to allow for rest seat preparation
intraorally
Critical Review of Some Dogmas in Prosthodontics (Carlsson 2009)
1. Kayser, in 1981, published his opinions on the shortened dental arch (SDA). His message was that there is
sufficient adaptive capacity in subjects with SDA when
at least four occlusal units are left. Kayser’s and his successor’s research groups have conducted a series of
clinical cross-sectional and longitudinal studies on
SDA.
2. The World Health Organization guidelines published
in 1992 provided strong support by suggesting that
the SDA concept was a possible clinical alternative in
situations when economy and service resources are
limited.
6. The indications for the ‘copy denture’ technique
include:
a. Recurrent fracture of a previous upper denture base
b. A spare set of satisfactory dentures
c. An elderly patient who has worn a satisfactory set
of dentures for many years
d. Incorrect positioning of the anterior teeth
e. Replacement of immediate dentures
7. The choice of denture teeth:
a. Is dependent on the age of the patient
b. Is dependent on the patient’s complexion
c. Should be determined by the patient
d. Should conform to the patient’s facial contour
e. Is related to the upper lip length
8. The neutral zone technique:
a. Can be used in the maxilla
b. Should have the upper denture in place while it is
being recorded
c. Is used to record the zone of minimal conflict
d. Helps to determine the pre-extraction position of
the natural dentition
e. Requires the use of laboratory stents to locate the
teeth
9. Elastic impression materials include:
a. Plaster
b. Alginate
c. Zinc oxide/eugenol
d. Agar
e. Silicone
10. At the jaw registration stage in complete dentures:
a. The freeway space of the dentures should be deter-
mined
b. The horizontal relationship of the jaws is recorded
c. The tooth shade is chosen
d. The tooth mould is selected
e. Heat-cured base plates may provide increased stability
11. Surveying for partial denture construction:
a. Is only carried out on the preliminary model
b. Is always carried out at 90° to the occlusal plane
c. Should use an analysing rod prior to deciding the
angle of survey
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Master Dentistry
d. Determines naturally occurring guideplanes
e. Is not necessary in acrylic partial denture construction
12. Various techniques used in the management of the
free-end saddle situation include:
a. Split-cast technique
b. RPI (rest, plate, I bar) design
c. Altered cast technique
d. Balance of forces
e. Flexible connectors
EXTENDED MATCHING ITEMS QUESTIONS
Theme: Partial dentures
For each of the statements (a–e), select from the list below
(1–10) the single most appropriate component or function
of component of partial dentures that matches the statement. Each diagnosis may be used once, more than once or
not at all:
1. Saddles
2. Support
3. Occlusal rests
4. Retention
5. Bracing
6. Stability
7. Reciprocation
8. Connector
9. Indirect retention
10. Clasps.
a. The resistance to vertical force directed towards the
mucosa.
b. The resistance to horizontal forces provided by rigid
components of the denture.
c. Function, anatomical constraints, hygiene, rigidity
and patient acceptability all influence the choice of
what?
d. This resists pivotal movement of a denture through
the hinge axis of the clasp tips.
e. The principle of horizontal resistance to tooth move-
ment that may occur during clasp engagement.
Fig. 4.6 60-year-old male with loose upper denture.
Fig. 4.7 Ulcerated lower arch of a 50-year-old female.
CASE HISTORY QUESTIONS
Case History 1
A 60-year-old male presents complaining of a loose upper
denture. He has been edentulous for over 20 years and has
had two sets of complete dentures in this time. On examination, his palate presents as seen in Fig. 4.6.
1. What questions in the history of this patient are
important in this problem?
2. What are the priorities in the management of this
patient?
3. What are the differential diagnoses?
Case History 2
A 50-year-old lady presents with an unretentive upper denture and a lower denture that causes recurrent ulceration
(Fig. 4.7).
1. What are the likely causes for the symptoms that this
patient presents with?
2. How could you resolve the problem of the unretentive
upper denture?
3. What treatment would be suggested to resolve the
problems of her lower arch?
SHORT NOTE QUESTIONS
Write short notes on:
1. disinfection of impression materials
2. special trays
3. heat-cured base plates
4. the important features in complete denture construction
that contribute to the retention of a denture, naming
three anatomical features that may affect the retention
of complete dentures
5. an Every denture design
6. gingival stripping caused by partial dentures
7. spoon dentures
4 • Prosthodontics
135
8. the properties that a clasp should exhibit and list three
commonly utilised materials used to construct denture
clasps
9. denture stomatitis
10. angular cheilitis
11. denture hygiene.
Self-Assessment: Answers
MULTIPLE CHOICE ANSWERS
1. a. True. A history of tooth loss will provide an approxi-
mate timescale for the resorptive processes of that
individual patient.
b. True. A denture history will give some indication as
to the tolerance of the patient to a prosthesis.
c. True. A medical history may provide information re-
garding current medication that could result in a dry
mouth and, therefore, affect the possible retention of
a prosthesis. Several other factors in a medical history may also affect complete denture construction.
d. True. A history of smoking and/or drinking will in-
crease the prevalence of oral malignancy and may
necessitate more frequent reviews to monitor the oral
mucosa.
e. True. It is important to assess the patient’s expecta-
tions as these can often be unrealistic and may affect
the patient’s acceptance of a prosthesis.
2. a. True. Because stearic acid improves flow properties
of material.
b. False. Borax is used as a retarder in gypsum products.
c. True. Talc increases the viscosity of the material,
reducing its thermal contraction.
d. True. Determines the softening temperature.
e. False. Copper is metallic and is not an impression
compound.
3. a. True. An immediate denture can provide an aesthetic
replacement of an anterior tooth.
b. False. An immediate denture would not be indicated
as the bone contour of the area after surgical intervention is uncertain.
c. True. An immediate denture can be used as a space
maintainer.
d. False. It is rarely necessary unless an addition to an
existing partial denture can be carried out to replace
a posterior unit in this manner.
e. True. Although this point is often one of debate, it is
generally accepted that an immediate denture can
assist in haemorrhage control if constructed carefully.
4. a. True. A cast cobalt–chromium clasp of this length
will not be flexible enough to engage an undercut.
b. False. A gold clasp is more flexible.
c. False. Engages a 0.25 mm undercut.
d. True. Partial dentures themselves could be consid-
ered as food traps but the clasp component particularly causes a problem.
e. True. These are the three traditional designs of clasp
arm.
ESSAY QUESTION
List the basic principles of removable partial denture design
and describe their importance in relation to the maintenance of oral health.
5. a. True. This is the concept of the altered cast technique.
b. False. That is the split-cast technique.
c. False. This is not the purpose of the technique.
d. True. This is how an altered cast is carried out.
e. False. This is not the purpose of the technique.
6. a. False. The reason for the recurrent fracture of
the denture base would need to be addressed prior
to remaking the denture.
b. True. This is a method of duplicating dentures.
c. True. If a patient has become accustomed to the
polished surfaces of an existing denture then it is
often advantageous to copy this.
d. False. There would be no advantage of a copy tech-
nique if the tooth position had to be changed.
e. True. This would mean that the original tooth posi-
tion was copied.
7. a. True. The age of the patient will dictate tooth colour and length.
b. True. This will determine tooth colour.
c. False. Often patients will choose tooth colour to be
too white; therefore, their approval should be
sought after the dentist’s selection.
d. True. This will help to determine the tooth mould.
e. True. The length of the upper incisors will be partly
determined by the upper lip length.
8. a. False. The neutral zone can only be used in the
mandible.
b. True. Upper lip support is essential to record the
neutral zone.
c. True. The neutral zone is often called the zone of
minimal conflict.
d. True. The technique helps to determine the likely
position of the original dentition.
e. True. This is how the technician positions the teeth
from the neutral zone impression.
9. a. False. Plaster is a non-elastic impression material.
b. True. Alginate is an elastic impression material.
c. False. Zinc oxide/eugenol is a non-elastic impres-
sion material.
d. True. Agar is an elastic impression material.
e. True. Silicone is an elastic impression material.
10. a. True. The occlusal face height of the denture should
be recorded at the jaw registration stage.
b. True. The relationship of the mandible to the max-
illa in the retruded contact position is recorded.
c. True. The technician needs this information for the
try-in stage.
d. True. The technician needs this information for the
try-in stage.
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Master Dentistry
e. True. The use of heat-cured bases does provide
a more stable record rim for the registration
stage.
11. a. False. The master model has to be surveyed also.
b. False. Although this is often the first choice of sur-
vey, it is often the case that the path of insertion
should follow a different path.
c. True. The use of an analysing rod helps to assess
the path of insertion prior to the initial survey.
d. True. The use of naturally occurring guideplanes
will aid greatly in the retention of a denture.
e. False. Undercut areas must be blocked out prior to
processing an acrylic partial denture.
12. a. False. This technique is used to remount casts after
processing.
b. True. The use of a mesial rest, distal plate and I bar
design is commonly applied in this situation.
c. True. The altered cast can be used to address this
clinical situation.
d. True. This design concept has been used in the free-
end saddle situation.
e. True. The use of stress-breaking or flexible connec-
tors can be used in this clinical situation.
EXTENDED MATCHING ITEMS ANSWERS
a. 2
b. 5
c. 8
d. 9
e. 7
CASE HISTORY ANSWERS
Case History 1
1. History taken would reveal:
n
social history: this patient was a heavy smoker who
smoked around 60 cigarettes a day. He was also a
heavy drinker.
n
dental history: the patient had experienced surgery to
his front teeth prior to their extraction 10 years ago.
The lesion in his palate was first noticed 6 months ago
and has progressively got larger since then resulting
in his denture no longer fitting.
n
medical history: this may have some relevance to the
problem but did not in this case.
2. Resulting from this patient’s presentation and history, it
is unlikely that the lesion in the palate is a simple traumatic ulcer and, therefore, an urgent referral to an oral
maxillofacial surgeon or an incisional biopsy must be
carried out. The suggestion that the denture should be
left out for a week and the situation reviewed given the
history and presentation of the lesion would be ill-advised.
3. Differential diagnosis. The main palatal lesion was an
adenoid cystic carcinoma, but it could have been a squamous cell carcinoma, a pleomorphic adenoma or a mucoepidermoid carcinoma. The histological appearance
would have confirmed the diagnosis. The lesion on the
ridge was an amalgam tattoo.
Case History 2
1. The upper denture problem is likely to be related to a
flabby ridge that has developed as a result of the retention of the lower natural dentition. This often results in
the patient having a problem of support or stability of
the denture, although there can also be a problem of
retention. The recurrent oral ulceration of the lower
ridge is likely to be a result of an unretentive and unstable lower denture caused by the lack of denturebearing area and also the height discrepancy between
the occlusal plane and the residual ridge.
2. The management of an unsupported or flabby ridge is by
use of a selective compression impression technique or
the use of a mucostatic impression technique. A brief
summary of these two techniques should be included.
3. The problem of the lower arch is complex; however, the
extraction of the remaining lower dentition may just
transfer the problem from that of a partial denture
problem to one of a complete lower denture problem.
This particular case was managed by root filling the
lower canines and using stud attachments to retain an
acrylic partial lower denture. This solved the presenting
complaints because the stud retainers stopped the
movement of the lower denture, thus eliminating the
traumatic ulceration.
SHORT NOTE ANSWERS
1. Answer should include a summary of the guidelines on
the disinfection of dental impressions (Control of Substances Hazardous to Health Regulations 1999). An impression should be rinsed under running water on removal from the mouth to remove any saliva, blood or
debris. The impression should then be disinfected. Possible disinfectant solutions should be listed and the duration of soak stated (e.g. sodium hypochlorite 10 000 ppm
for 5 minutes minimum). The effects of such disinfectants
on the stability of the impression material should also be
commented on.
2. Special trays are constructed of a variety of materials
including shellac, acrylics and light-cured composite
materials. The use of adhesives can be complemented by
the addition of perforations within the tray design.
Trays should be extended ideally to 2 mm short of the
functional sulcus depth. The spacing of a tray is dependent on the impression material being used and varies
from 3 mm spacing for impression plaster to 0.5 mm for
zinc oxide/eugenol.
3. Heat-cured base plates can be used at the jaw registration stage of complete denture construction. They provide increased stability to the denture for use at this
stage and give a good guide to the likely retention and
stability of the completed denture. They potentially can
have disadvantages in that if there is minimal interarch
space then premature contact of the base plates between the maxillary tuberosity region of the upper
plate and the retromolar pad region of the lower can
occur. The processing of the final denture can potentially cause distortion of the base plate if it is not carried
out carefully.